#include <stdio.h>
#include <stdlib.h>
#include <math.h>

typedef struct {
    float x,y;
} point;

double pdist(point a,point b)
{
    float m=(a.x-b.x)*(a.x-b.x);
    float n=(a.y-b.y)*(a.y-b.y);
    m=m+n;
    return m;
}

double area(point a,point b,point c)
{
    float m=pdist(a,b);
    float n=pdist(a,c);
    m=m*n;
    m=sqrt(m);
    m=m/2;
    return m;
}

int main()
{
    point a,b,c;
    scanf("%f %f %f %f %f %f",&a.x,&a.y,&b.x,&b.y,&c.x,&c.y);
    printf("%.7lf", area(a,b,c));
    return 0;
}